Sealing device for high vacuum furnace



p 1967 H. w. WESTEREN 3,342,469

SEALING DEVICE FOR HIGH VACUUM FURNACE Filed Feb. 8, 1965 3 2Sheets-Sheet 1 5 i4 /4 /0 /Z 34 30 INVENTOR. fifrerf W it/asreraz 9/ YMJM 4 /10772 e ys.

Sept. 19, 1967 H. w. WESTEREN 3,342,469

SEALING DEVICE FOR HIGH VACUUM FURNACE Filed Feb. 8, 1965 2 Sheets-Sheet2 'Hi- 5 /E5 HHI/ /E6 l I 1 INVENTOR. flkrer'z W wafer??? United StatesPatent 3,342,469 SEALING DEVICE FOR HIGH VACUUM FURNACE Herbert W.Westeren, Barrington, R.I., assignor to C. I. Ilgayes, Inc., Providence,R.I., a corporation of Rhode land Filed Feb. 8, 1965, Ser. No. 430,989 3Claims. (Cl. 263-36) The present invention relates to a high vacuumelectric furnace. More particularly, the present invention relates to asealing device for use in a high vacuum electric furnace, wherein theheating chamber located within the furnace is effectively sealed duringloading of work pieces in the furnace and unloading of work piecestherefrom after the heat treatment cycle.

In the prior known vacuum furnaces, it was the usual practice to place abatch of the articles to be heat treated within the furnace heatingchamber, after which the heating chamber was evacuated and then heatedto a prescribed temperature for heat treating the articles therein for apredetermined period of time. After the heating cycle was completed, thearticles were effectively cooled and then the vacuum within the furnacewas broken for the purpose of removing the heat treated work piecestherefrom.

Since it is desirable to maintain the heating chamber of the furnaceunder vacuum and at the heating temperature at all times, therebyproviding for greater capacity of articles being heat treated, thepresent invention provides for continuous-1y maintaining the heatingchamber of the furnace under vacuum and at a prescribed temperatureafter removal of the heat treated articles therefrom and during loadingand unloading of the articles to and from the furnace. Because of thehigh temperatures generated in the heating chamber, the usual sealingelements such as silicone, rubber, etc., are not practical for use withthe door of the heating chamber for the sealing thereof.

In order to accomplish the purpose of maintaining the heating chamber ofthe furnace under continuous vacuum and high level temperatures, thepresent invention employs a unique metal-to-metal seal that provides forsealing the door of the heating chamber from an outer compartment intowhich the work pieces are loaded or unloaded therefrom. Since it is notpractical to employ an insulation type seal for the door of the heatingchamber of the furnace embodied herein, the metal-to-metal sealincorporated herein includes an annular sealing flange through which abore extends for communication with the interior of the chamber of thefurnace. The outer face of the annular sealing flange is formed with aseries of concentric grooves, the centermost of which is substantiallygreater in depth and cross-sectional dimension than that of theremaining grooves. The spaces between the grooves define annular landsthat are co-extensive with the face of the flange and are adapted tocooperate with a circular sealing plate for making metal-to-metalsurface contact therewith. The annular grooves located adjacent to thelarger grooves form labyrinth-type seals that 00- operate with thelarger groove to effectively seal the interior of the heating chamber.Since the heating chamber is under vacuum, the normal tendency ofatmosphere contained in the outer compartment of the furnace would be toleak through the seal and into the bore formed in the annular sealingflange that communicates with the interior of the heating chamber. Inorder to prevent such leakage, the larger groove formed in the outerface of the annular sealing flange is placed in communication with asource of vacuum, such as a vacuum pump. The larger groove is thusevacuated to a vacuum pressure that corresponds generally to the vacuumconditions of the heating chamber. Any atmosphere that tends to leakthrough the labyrinth seal formed by the sealing plate and the annularsealing flange will then be trapped in the larger groove and will beevacuated before it can leak into the bore of the sealing flange andthen into the interior of the heating chamber.

Accordingly it is an object of the present invention to provide afurnace in which the heating chamber thereof may be maintainedcontinuously under vacuum and at a prescribed temperature level whilework pieces are loaded into the furnace or removed therefrom.

Another object of the invention is to provide an effective, yetinexpensive meta-l-to-metal vacuum seal for sealing the heating chamberof a high vacuum furnace.

Still another object is to provide a seal for use in a high vacuumfurnace that includes a plurality of annular grooves that define alabyrinth-type seal, one of the annular grooves having communicationwith a vacuum source for evacuating the groove and thereby preventingingress of atmosphere through the labyrinth seal.

Still another object is to provide a metal-to-metal seal for use in ahigh vacuum furnace, wherein a metallic sealing plate is remotelycontrolled for movement into sealing engagement with an annular sealingflange that defines a door for the heating chamber located in the highvacuum furnace.

Still another object is to provide a high vacuum furnace havingexternally control-led transfer apparatus for moving a load supportmember and articles carried thereby to and from a heating zone and forfurther moving the support member in a manner to transfer the articlesto a quench tank after the heat treatment thereof.

Other objects, features and advantages of the invention will becomeapparent as the description thereof proceeds when considered inconnection with the accompanying illustrative drawings.

In the drawings which illustrate the best mode presently contemplatedfor carrying out the present invention:

FIG. 1 is a vertical sectional view with parts shown in elevation of thefurnace construction embodied in the present invention;

FIG. 2 is a sectional view taken along lines 2-2 in FIG. 1;

FIG. 3 is a sectional view taken along FIG. 1;

FIG. 4 is a front elevational view of the annular sealing flangeembodied in the present invention;

FIG. 5 is a sectional view of the sealing flange illustrated in FIG. 4and showing the coaction of the sealing plate therewith;

FIG. 6 is a sectional view taken along lines 6--6 in FIG. 1; and

FIG. 7 is a perspective view showing the control means and trough joinedthereto on which the articles to be heat treated are mounted, thecontrol means being actuated externally of the furnace for movement ofthe trough into the heating chamber of the furnace.

Referring now to the drawings and more particularly to FIG. 1, a highvacuum heat treatment furnace of. the coldwall type is illustrated andis generally indicated at 10. The heat treatment furnace 10 iselectrically heated, as will be described hereinafter, and may beevacuated to microns and less, being normally operated at approximately10- 10'" mm. Hg. As illustrated in FIG. 1, the furnace 10 includes aheating chamber generally indicated at 12, an outer compartmentgenerally indicated at 14 and communicating with the heating chamber 12,and an outer housing generally indicated at 16 that communicates withthe compartment 14 and that defines the area in which load pieces to beheat treated are inserted and withdrawn therefrom and further includesmeans for quickly quenching the heat treated articles that are removedfrom the heating chamber 12.

lines 3-3 in The heating chamber 12 is defined by a cylindrical section18 to which an end wall 20 is secured. The end wall 20 sealingly engagesa flange 22 and has joined thereto a dome 24 the interior of which maybe Water cooled if it is so required. A-plurality of fastening elements26 are employed for securing the end wall 20 and dome 24 to the sealingflange 22. Mounted in sealing engagement at the other end of thecylindrical section 18 is an end wall 28 that is secured to an endflange 30 by a plurality of fastening elements 32. An annular jacket 34envelops the cylindrical section 18 and is adapted to receive a coolingliquid therein for maintaining the walls of the cylindrical section at atemperature level that is safe for handling of the apparatus. The jacket34 further provides for rapid cooling of the heating chamber whenrequired.

As mentioned 'hereinabove the interior of the furnace construction isadapted to be evacuated during the heat treatment cycle, and for thispurpose the cylindrical section 18 is provided with an enlarged exhaustport 36 with which a pipe 38 communicates. The pipe 38 is secureddirectly to the cylindrical section 18 and is provided with an outerflange 40 for securement to a corresponding flange that is, in turn,connected to suitable evacuating equipment.

Located interiorly of the heating chamber 12 is a heating unit generallyindicated at 42 that includes a plurality of woven graphite flexibleheating elements 44 that are secured to terminals one of which isindicated at 46 by segments 48. The opposite end of the heating elements44 are interconnected by a conducting ring 50. Suitable openings areformed in the cylindrical section 18 with which mounting sleeves 52communicate for receiving the terminals therethrough.

As described above, the woven graphite heating elements 44 define aheating zone therebetween. In order to insulate this heating Zone so asto obtain the maximum benefit for the work being heat treated within theheating zone, an insulating material indicated at 58 is also providedand is located in surrounding relation with respect to the heatingelements 44. The insulating material is defined by a plurality of layersof graphite felt material, the layers being formed in annular relationto define walls as illustrated in FIG. 1. A plurality of rods 59 extendthrough the side layer of the insulating material 58 and are secured toa plate 60 at one end of the heating zone and to another plate 62located at the other end of the heating zone. In connection with thespecific construction of the heating chamber 12, reference is made tothe ,copending application Serial No. 262,686 filed March 4, 1963.

The furnace is supported in position by spaced pedestals 64 that aresecured to the exterior surfaces of the heating chamber 12 and by .thelower end of the outer housing 16. Disposed intermediate the outerhousing 16 and the heating chamber 12 is the outer compartment 14 thatis defined by the end Wall 28, an opposing wall 66, a top wall 68 and abottom wall 70, the top wall 68 and bottom wall 70 being secured to theend walls 28 and 66. Extending into the interior of the outercompartment 14 and formed as part of the end wall 28 is a pipe 72 towhich an annular flange 74 is joined, The annular flange 7.4 is inclinedwith respect to the vertical and is provided with a bore 76 therein thatcommunicates with the interior of the pipe 72 and the cylindical section18 of the heating chamber 12.

The annular flange 74 defines a port through which the articles to beheat treated are inserted and is adapted to be sealed after the heattreatment cycle and removal of the articles from the interior of theheating chamber 12. For this purpose the annular flange 74 is formed insuch a manner so as to cooperate with a sealing plate 77 for eflectivelysealing the interior of the heating chamber 12. Referring now to FIGS. 4and 5, the annular flange 74 is illustrated in detail and includes abody portion 78 in which the bore 76 is formed. The .outer surface ofthe body 78 is formed with a plurality of concentric annular groovesthat are formed in pairs around an enlarged central groove. Thus asshown in FIGS. 4 and 5 outer annular grooves 80 and 82 surround anenlarged annular groove 84 as opposed to the interior annular grooves 86and 88. The annular grooves 80 and 82 cooperate with the enlargedannular groove 84 to define annular lands 88, 90 and 92, while theinterior annular grooves 86 and 87 cooperate with the enlarged annulargroove 84 to define lands 94, 96 and 98. As will be describedhereinafter, the sealing plate 77 is adapted to be placed inmetal-tometal engagement with the lands defined by the annular groovesand thus form a seal therewith. The annular grooves 80, 82, 84, 86 and87 define a labyrinth seal with the sealing plate 77 and eliminate therequirement of the usual flexible sealing construction such as siliconeor rubber normally associated with seals in high vacuum apparatus. It isunderstood that the use of the heretofore known flexible seals is notpractical in the present invention because of the high temperatures thatare associated with the apparatus described herein.

In the operation of the furnace 10, after removal of the heat treatedarticles from the heating chamber 12, the sealing plate 77 is moved intoengagement with the face of the sealing flange 74 and thereafter thevacuum that is present in the outer compartment 14 and the housing 16 isbroken so that the heat treated articles may be re moved from thefurnace and additional articles inserted therein without breaking thevacuum within the heating chamber 12. Since the areas surrounding theannular sealing flange 74 are subjected to atmosphere or pressures aboveatmosphere, a tendency for the atmosphere to leak through the labyrinthseal of the annular flange and into the bore 76 for entry into theinterior of the heating chamber 12 is present. In order to eliminate anytendency of leakage through the annular flange 74, the enlarged annulargroove 84 is placed into communication with a source of vacuum such as avacuum pump by means of a pipe 100. With the space defined by theannular groove 84 under vacuum, any tendency of atmosphere to leakthrough the annular grooves 86 and 87 and then through the grooves 80and 82, will be prevented, since the atmosphere that may have leakedthrough the grooves 86, 87 will be quickly pumped out through pipe 100by the vacuum pump communicating therewith. The annular groove 84 isformed sufliciently large enough to provide an enlarged vacuum area thatwill trap leaking atmosphere therein for evacuation through the pipe100. The leak rate across the annular grooves 86 and 87 and thecorresponding lands 94, 96 and 98 is thereby efiectively reduced forpreserving the vacuum that is maintained Within the interior of theheating chamber 12.

In order to evacuate the outer compartment .14 and the interior of theouter housing 16 and to further supply an atmosphere under pressuretherein where required, the pipe 102 is provided and extends through thebottom wall 70 of the outer compartment. Connected to the pipe 102 by acoupling 104 is a pipe 106 that communicates with a source of vacuumsuch as a vacuum pump. A valve 108 is adapted to control communicationof the pipe 106 with the pipe 102 and is operated concurrently with avalve 110 that controls communication of a pipe 112 with the pipe 102.An atmosphere under pressure may be introduced through the pipe 112 andvalve 110 for entry into the compartment 14 and housing 16 when thevacuum is broken therein.

Since the extension 72 of the wall 28 is located in communication withthe heating chamber 12, together with the wall 28, cooling coils 114through which a cooling liquid is circulated are placed into contactwith extension 72 and the wall 28.

As hereinabove, stated, movement of the sealing plate 77 is adapted tobe remotely controlled for placing the plate in contact with the sealingflange 74. For this purpose the sealing plate 77 is connected to a lever116 that is in turn joined to a bar 118 through which a shaft 120extends. The shaft 120 projects through the sealing gland 122 in thewall 66 and is provided with a handle 124 on the outer end thereof. Itis seen that manipulation of the handle 124 will move the bar 118 andlever 116 for positioning the plate 77 in proper sealing relation on theface of the sealing flange 74.

It is seen that there is no requirement for utilizing clamps, bolts, orother positive locking elements for sealing the plate 77 to the sealingflange 74. Thus, after the" handle 124 has been operated to locate theplate in proper sealing position on the sealing flange 74 and thepressure in the compartment 14 is brought to atmospheric, the pressuredifferential produced between the heating chamber 12 and the compartment14 will be sufficient to lock the plate 77 in place. The seal across thesealing flange 74 is then effectively maintained by means of thelabyrinth seal defined by the grooves 80, 82, 86 and 87, the lands 88,90, 82, 84 and 86, the large annular groove 84, and the plate 77.

Although various techniques may be employed for inserting the workpieces to be heat treated into the heating chamber 12, as shown in FIGS.1, 2 and 7 a track assembly is utilized on which the work supportdefined by a trough 126 is mounted. The track assembly includes a firsttrack 128 that extends through the housing 16 and into the compartment14. Disconnected from the first track section 128 and extending from theinterior of the bore 76 into the heating zone of the heating chamber 12is a second track section 130. Since the heating chamber 12 must becompletely enclosed after withdrawal of the work pieces therefrom thetrack section 128 and 130 are disconnected as indicated. Although notshown in detail, it is understood that the track sections 128 and 130are suitably supported in position within the furnace 10. The trough 126is mounted for movement on the track sections 128 and 130 and in orderto accomplish movement of the trough from a position exteriorly of thechamber 12 an actuating rod 132 is connected to the rear end of thetrough and includes a handle 134 that is joined to the outermost endthereof. The first track section 128 is located at a load and unloadstation in the housing 16 and as seen in FIGS. 1 and 2 the housing 16 isdefined by the Wall 66, a forward wall 136, side walls 138- and 140, abottom wall 142 and a removable loading door 144. A directing chute 146is located within the upper part of the housing 16 below the door 144and provides for directing work pieces into the trough 126. A quenchtank 148 is located within the housing 16 below the track section 128'and includes a quench basket 150 therein into which the heat treatedarticles are directed after the heat treatment thereof. A bafileconstruction indicated at 152 is also formed as part of the quench tank148 and prevents vaporized quenching medium from escaping from thequench tank 148. It is seen that after the articles to be heat treatedare loaded into the trough 126, the trough is moved on the track section128 and then onto the track section 130 for placement within the heatingZone of. the heating chamber 12. During movement of the trough 126 tothe heating zone, it is understood of course that the sealing plate 77is located in the open position thereof as seen in dotted lines in FIG.1.

In operation after the articles to be heat treated are placed on thetrough 126 and before movement into the heating zone within the heatingchamber 12 the compartment 14 and housing 16 are evacuated. The interiorof the heating chamber 12 is maintained at the prescribed temperaturelevel and the area therein is continuously evacuated by the vacuum pumpthat is interconnected to the heating chamber 12 through the pipe 38 andport 36. In order to evacuate the compartment 14 and housing 16, thevalve 112 connected to the atmosphere source is closed and the valve 108is opened so that the pipe 102 is placed into communication with thevacuum pump for the evacuation of the compartment 14 together with theinterior of the housing 16. It is understood, of course, that the door144 is located in closed position after loading of the articles on thetrough 126. The sealing plate 77 is then opened after the compartment 14and housing 16 are evacuated to receive the trough and articles there onfor entry into the heating chamber 12. After completion of the heatingcycle, the trough 126 and the articles thereon are withdrawn from theheating chamber into the housing 16, at which point the articles in thetrough 126 are engaged by the chute 146, which knocks the articles offthe trough and into the quench tank 148 for quick quenching thereof. Asdescribed in copending application Ser. No. 422,617, filed Dec. 31,1964, the quick quench ing of the heat treated articles whilethe'articles are continuously exposed to a vacuum prevents thecontamination of the surfaces thereof and provides a bright appearingsurface.

After the articles have been dumped into the quench tank 148, and thebasket 150 therein removed, the sealing plate 77 is once again movedinto contact with the sea1- ing flange 74 to effectively seal theinterior of the heating chamber 12. It is at this time that the valve108 is closed and the valve 110 opened to admit atmosphere into thecompartment 14 and the housing 16. This breaks the vacuum in thecompartment 14 and housing 16 and the door 144 may then be opened forplacement of additional articles to be heat treated into the trough 126.After placement of the articles to be heat treated in the trough 126,the valve 110 is again closed and the valve 108 opened to effectivelyevacuate the interior of the compartment 14 and the housing 16. Duringthe interim period that the compartment 14 and housing 16 was exposed toatmosphere, the annular groove 84 in the sealing flange 74 was beingevacuated through the pipe 100. Evacuation of this groove effectivelyprevented leakage of the at mosphere through the labyrinth seal in thesealing flange defined by the grooves 80 and 82. After the compartment14 and the housing 16 are evacuated through the pipe 102, the plate 77is withdrawn from the sealed position thereof by manipulation of thehandle 124 and the trough 126 with the articles thereon, may then bemoved on the track sections 128 and 130 to place the trough 126 and thearticles thereon within the heating zone in the heating chamber 12.

While there is shown and described herein certain specific structureembodying the invention, it will be manifest to those skilled in the artthat various modifications and rearrangements of the parts may be madewithout departing from the spirit and scope of the underlying inventiveconcept, and that the same is not limited to the particular forms hereinshown and described, except insofar as indicated by the scope of theappended claims.

What is claimed is:

1. In a furnace for use in heat treating metallic articles, a heatingchamber in which said articles are heat treated at relatively hightemperatures, a compartment communicating with said heating chamber andreceiving said articles prior to introduction into said heating chamberand after the heat treating operation, a metal sealing member locatedbetween said heating chamber and compartment and having a bore formedtherein that provides communication between said heating chamber andcompartment when said articles are moved to and from said heatingchamber, said metal sealing member being subected to the hightemperatures generated in said heating chamber, means for controllingthe pressure in said heatmg chamber and compartment during the heatingcycle of said articles wherein the pressure in said heating chamber isthe same as that maintained in said compartment, a metal sealing platethat is movable into engaging relation with said sealing member whensaid bore is to be sealed for maintaining the temperature and pressurein sa d heating chamber, the face of said sealing member with which saidsealing plate engages having a cavity formedfherein, a vacuum sourcecommunicating with Said CaVItY for Posmg a negative pressure thereinwhen sa d pl t s n e a m n wi h a ea g m b s wherein a vacuumseal isformed across the engaging p01.- tions of said sealing member and plate,said sealing memher being free of sealing materials so that there isonly metal-to-metal contact between said plate and sealing member andthe heat to which the sealing member is subjected is transferred to saidsealing plate, means for introducing a gaseous medium into saidcompartment after said plate has been placed in contact with saidsealing member for increasing the :pressure in said compartment, saidsealing plate being sealed to said sealing member by the differentialpressure between the heating chamber and compartment when said sealingplate is.engaged with said sealing member, and means for moving saidplate into ,and out of contact with said sealing member.

2. In a furnace as set forth in claim 1, a plurality of grooves formedin the face .of said sealing member, said grooves cooperating with saidcavity to define lands therebetween, the grooves and lands forming alabyrinth :3 seal with said cavity between said sealing member andplate.

3. In a furnace as set forth in claim 2, said cavity that communicateswith a vacuum source being greater in cross-sectional dimension thanthat of the other gr oves and being located substantially coaxial in theface of said sealing member and in surrounding relation with respect tosaid bore.

References Cited UNITED STATES PATENTS 2,459,295 1/1949 Skoog 34-242 X3,144,035 8/1964 Hablanian et a1. 34242 X 3,172,994 3/1965 Peay et al263-40 X 3,183,937 5/1965 Earley et al -34242 X 3,222,043 12/1965Troglione et al. 34 -242 X FREDERICK L. MATTESON, JR., Primary Examiner.D. A. TAMBURRO, Assistant Examiner.

1. IN A FURNACE FOR USE IN HEAT TREATING METALLIC ARTICLES, A HEATING CHAMBER IN WHICH SAID ARTICLES ARE HEAT TREATED AT RELATIVELY HIGH TEMPERATURES, A COMPARTMENT COMMUNICATING WITH SAID HEATING CHAMBER AND RECEIVING SAID ARTICLES PRIOR TO INTRODUCTION INTO SAID HEATING CHAMBER AND AFTER THE HEAT TREATING OPERATING, A METAL SEALING MEMBER LOCATED BETWEEN SAID HEATING CHAMBER AND COMPARTMENT AND HAVING A BORE FORMED THEREIN THE PROVIDES COMMUNICATION BETWEEN SAID HEATING CHAMBER AND COMPARTMENT WHEN SAID ARTICLES ARE MOVED TO AND FROM SAID HEATING CHAMBER, SAID METAL SEALING MEMBER BEING SUBJECTED TO THE HIGH TEMPERATURES GENERATED IN SAID HEATING CHAMBER, MEANS FOR CONTROLLING THE PRESSURE IN SAID HEATING CHAMBER AND COMPARTMENT DURING THE HEATING CYCLE OF SAID ARTICLES WHEREIN THE PRESSURE IN SAID HEATING CHAMBER IS THE SAME AS THE MAINTAINED IN SAID COMPARTMENT, A METAL SEALING PLATE THAT IS MOVABLE INTO ENGAGING RELATION WITH SAID SEALING MEMBER WHEN SAID BORE IS TO BE SEALED FOR MAINTAINING THE TEMPERATURE AND PRESSURE IN SAID HEATING CHAMBER, THE FACE OF SAID SEALING MEMBER WITH WHICH SAID SEALING PLATE ENGAGES HAVING A CAVITY FORMED THEREIN, A VACUUM SOURCE COMMUNICATING WITH 